Development rate and gene expression of IVP bovine embryos cocultured with bovine oviduct epithelial cells at early or late stage of preimplantation development

The use of somatic cells for coculture with embryos has been amply investigated to study embryo maternal interactions. The use of bovine oviduct epithelial cells (BOEC) has been shown to improve blastocyst rate and quality, affecting their gene expression profile. In this study, we evaluated different timing of BOEC coculture for the development of in vitro produced embryos, and their effects on blastocysts rate and mRNA abundance of some genes important for embryo development. Our results confirmed the positive effects of BOEC on early development of bovine embryos. The presence of the cells during the first four days or during the last four days of development was enough to produce the full BOEC effect. When the presence of BOEC was restricted to the four first days, the kinetics of blastocyst development was accelerated, with significantly more blastocysts at days 6 and 7 than when cells were present all along the culture or only during the last four days. Older cells used at early stage were not active anymore. Using young cells at late stage did not improve the cell effect, compared to older ones. Therefore, the lower effect of BOEC at late stage, compared to early period, may not be explained by cell aging. In addition, the presence of BOEC, at early or late stages, induced changes in the embryos expression profile of genes known to be related to embryo quality, suggesting reduced apoptosis and increased capacity to struggle against oxidative stress after coculture. In conclusion, we confirmed the effect of BOEC on the rate and quality of bovine IVP embryos development. We showed for the first time that the presence of BOEC during the four first days of the 8 days development is enough to produce these effects. These first four days represent the period of the presence of the embryos in the oviduct in vivo, highlighting the physiological relevance of this in vitro model of coculture. In addition, we showed that the presence of BOEC at early stages of development induced modification of transcription profile in the blastocyst, four days later, suggesting an epigenetic regulation induced by BOEC in growing embryos.